In recent years, performance improvement of plastics has been increasingly demanded, and a number of polymers having various properties have been developed and offered to the market. In particular, liquid crystalline resins such as liquid crystalline polyesters having optical anisotropy, which are characterized by parallel arrangement of molecular chains, are attracting attention from the viewpoint of excellent moldability and mechanical properties, as well as insulation properties. Their use is expanding to electric/electronic parts and machine parts.
In particular, liquid crystalline polyesters composed of aromatic skeletons have especially excellent moldability, mechanical properties, and insulation properties. For example, for improvement of the melt moldability, liquid crystalline polyesters using aromatic diols in which nitrogen, sulfur, or phosphorus is contained and high-molecular-weight aromatic diols have been proposed (see, for example, Patent Documents 1 to 3). On the other hand, methods for producing liquid crystalline polymers in which aromatic sulfonic acids as catalysts are added to suppress generation of gas such as phenol gas, thereby suppressing resin color changes due to heat deterioration (for example, Patent Document 4), methods for producing copolymerized polyesters having specific structures in the presence of a sulfonic acid-based catalyst for improving heat resistance and mechanical properties (for example, Patent Document 5), and methods for producing liquid crystalline polyesters having specific structures for improving fluidity and retention stability (see, for example, Patent Document 6), have been proposed.